it's something educators call differentiated learning. some students work on basic skills while others advance to more challenging lessons. the learning lab allows a school to hire six fewer teachers, which rocketship says results in savings of up to half a million dollars. that money is used to pay teachers higher salaries, fund academic deans who help teachers get better, and train principals for future rocketship schools. but one thing the savings are not used for: art and music classes. >> i wish we could have art and music in the school but at the same time if you want your child to have that in their life you can make the effort to try and get it after school or on the weekends. >> reporter: the learning lab saves schools a lot of money, but there's just one problem: they're not really working. >> there's definitely an aspect of us kind of not knowing enough about what's going on in learning lab to be able to use that in our classrooms. >> we don't yet get data that says, "okay, teach this differently tomorrow because of what happen